Now a team of researchers in Britain and the US has come up with a revolutionary new aircraft design that could make a dramatic contribution to curbing climate change.

The SAX-40, which has been developed by the Cambridge-MIT Institute, is a radically different shape of aircraft.

Officially, it is what is known as a "blended wing". It has a tailless wedge-shaped body with two bat-wings.

The Silent Aircraft Initiative (SAI) team has succeeded in coming up with a radically quieter plane. Crucially, the SAX-40 is also 35% more fuel-efficient than any airliner currently flying.

The case for radical change is getting stronger

Prof Ann Dowling, SAI's UK team leader

Oil prices may no longer be the $78 a barrel they were a few months ago, but with high fuel costs likely to continue, fuel efficiency is a major factor in all airlines' calculations.

Yet none of this means the SAX-40 will necessarily be built. Ever since the Boeing 707 first flew in 1957 and ushered in the commercial jet age, airliners have changed very little in their basic appearance.

Airliners still consist of a tube-like fuselage, with two swept-back wings and engines slung underneath. (The world's first - but commercially unsuccessful - passenger jet aircraft, the DeHavilland Comet, had the engines integrated in its wing).

Innovation costs

There are good economic reasons why design has remained so conservative.

By making the fuselage a tube, aircraft-makers can easily build a family of larger or smaller variants, utilising many of the same parts.

And by sticking engines under the wings, it's easier to maintain them, or upgrade them halfway through an aircraft's 30-year lifespan.

Naturally, aircraft manufacturers have made considerable improvements in the past 50 years, for instance using composite materials and lighter, more efficient engines.

The Airbus A380 has run into difficulties in recent months

Yet future improvements to the basic design are getting harder to make, according to Professor Ann Dowling, professor of mechanical engineering at Cambridge University and SAI team leader in the UK.

"The case for radical change is getting stronger," she says.

"It's only through such a change that one can achieve step-changes in fuel burn."

But for aircraft manufacturers like Boeing or Airbus, any design changes need to produce a quick return on their investment.

Boeing is working on developing fuel cells to power aircraft air-conditioning and electrical systems. Currently, these are run off a plane's engines, reducing their efficiency.